1. Field of the Invention
The present invention relates to an image forming apparatus employing an electrophotographic process such as a laser printer, an electrophotographic copying machine and so on, and particularly to a color image forming apparatus employing an electrophotographic process.
2. Related Art Statement
As a color image forming apparatus employing an electrophotographic process, there have been widely employed a system in which toner images are formed color by color on a photosensitive body, the resultant toner images are primarily transferred onto an intermediate transfer body to form an overcolor toner image, and the images are transferred collectively onto a paper by a secondary transfer; and a quadruple tandem system in which in four image forming stations having a photosensitive body, toner images of respective colors are formed, and the toner images of respective colors are transferred in order onto a paper being conveyed by a conveying belt.
The aforementioned intermediate transfer body and the conveying belt normally have a cleaner for cleaning the surfaces thereof attached thereto. As for the intermediate transfer body, it is necessary to mount a cleaner thereon because a transferred and remaining toner remains on the surface thereof after the secondary transfer. Further, since a large quantity of toners is stuck to the intermediate transfer body or the conveying belt, in the circumstances as stated below, it is necessary to mount a cleaner. That is, {circle around (1)} When the paper jam occurs, a toner image becomes remained on the intermediate transfer body or a toner image erroneously becomes formed on the conveying belt. {circle around (2)} Where image density adjusting is carried out, there is carried out a printing operation for forming a patch image on the intermediate transfer body or the conveying belt.
In the circumstances as stated above, since high cleaning ability is required, a blade cleaning system is employed. The blade cleaning system is the technique widely employed heretofore as a cleaning system for the photosensitive body because that system is high in cleaning ability despite the low expenses.
It is contemplated that in order to improve the cleaning ability and prevent a blade from being burred, a lubricating agent such as zinc stearate, sodium stearate and the like is coated on the intermediate transfer body or the conveying belt. However, the lubricating agent becomes necessary as a consumption article, the running cost of the image forming apparatus increases, a lubricating agent coating mechanism becomes necessary, and the coating mechanism need be replaceable, as a result of which the construction of the image forming apparatus becomes complicated. Further, when a toner image moves into the lubricating agent coating mechanism, the coating mechanism is contaminated by the toner, giving rise to a problem such that the coating ability lowers. Furthermore, in case of the intermediate transfer system, there also occurs a problem that the secondary transfer ability lowers due to the sticking of a lubricating agent depending on material for a secondary transfer roller.
Further, it is contemplated that in case of the intermediate transfer system, the cleaning blade is mounted on not only the intermediate transfer body but also the secondary transfer roller, to plan the longer service life of the secondary transfer roller, and preventing the back of paper from being contaminated. However, since the secondary transfer roller has a high elasticity and is deformed relatively greatly, there also occurs a problem that a cleaning blade for the secondary transfer roller is often burred.